Centralized traffic control system for railroads



Aug. 22, 1939.

D. F. DE LONG CENTRALIZED TRAFFIC CONTROL SYSTEM FOR RAILROADS 5Sheets-Shee t 1 Filed Aug.

I||l|||||||| .III III I I 2 fissm m in 352 umumnoz i ni om m imupg 3:55amma:-

ATTORNEY D. F. DE LONG Aug. 22, 1939.

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR RAILROADS Filed Aug. 7, 1930 5Sheets-Sheet 2 BY Ego/2Z6 7 I! ream m om m mmo v5 25 go uSu @nulllllllllllllllIl-Illlllllllll 5 Sheets-Sheet 3 D. F. DE LONG Filed Aug.7, 1930 BY ltzwgloz CENTRALIZED TRAFFIC CONTROL SYSTEM FOR RAILROADSx269 m wwr Aug. 22, 1939.

u Fiwv 525.30

CONTROL SYSTEM FOR RAILROADS Filed Aug. 7, 1930 5 Sheets-Sheet 4 Aug.22, 1939. D. F. DE LONG CENTRALIZED TRAFFIC arm /l HOW N NE W k ll I I II UCmH ESNUNFEQEEUU ATTORNEY I Aug. 22, 1939'. D. F. DE LONG 2,170,129

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR mnnoms Filed Aug.. '7, 19:50 5Sheets-She et 5 4. First way 5econd Way Last Wa'.y Control OFFice Stan5101M" SFG'tIOH FIG.5..

TYPICAL TABLE OF CODES Code. Call Cbde. Respons ive Relay No. v A .B C 1Patented Aug. 22, 1939 UNITED STATES PATENT OFFICE CENTRALIZED TRAFFICCONTROL SYSTEM FOR RAILROADS Darrol F. De Long, Rochester, N. Y.,assignor to General Railway Signal Company, Rochester,

Application August 7, 1930, Serial No. 473,529

25 Claims.

This invention relates to centralized traffic con.- trolling systems forrailroads, and more particularly pertains to a code type communicationsystem, by means of which a dispatcher or operator may govern, from aconveniently located control office, the operation of a plurality oftraflic controlling devices located along a railroad, and is informed ofthe progress of trains and the operated conditions of such trafiiccontrolling devices.

It has been found expedient in governing the movements of trains over arailroad, to place the control of such train movements under thesupervision o-f an operator stationed at a convenient point along therailroad. In order that this supervision may be the most efiicient, itis desirable that an electric communication system be provided to enablethe operator to manually control the signals, switches, derails, and thelike located along the railroad, and also to inform the operator as tothe progress of trains and such other conditions as may be desirable. Insuch a system, the various track switches and derails are usuallyoperated by power, under the manual control of the operator, withsuitable provisions for approach locking means local thereto preventingtheir improper and dangerous operation; and the signals governingtraflic over the switches are automatically controlled by ad.- joiningtrack circuits in accordance with automatic signalling practice, subjectto the control of the operator, who may holdany such signal at stopirrespective of its automatic control, or may allow such signals toclear when the positions of trains are such as to make it safe to do so.The intermediate signals, which are be.- tween those signals at routedetermining points, are preferably provided only with automatic controlgoverned in accordance with trackway conditions.

The present invention relates more particularly to such a communicationsystem which is employed to enable the operator to condition at will, afunction control relay, for each traffic controlling device in theterritory under his supervision, in such a way that the signals,switches, derails, and the like may be moved to such positions as theoperator may desire, subr ject to the automatic control of thesignalling sys- 50 tem associated therewith which prevents their unsafeoperation. This function of the system is conveniently termed thetransmission of controls.

The communication system, constituting more particularly the subjectmatter of this invention,

is further utilized to transmit to the operator the position of thevarious traffic controlling devices, the occupancy of certain trackcircuits and such other conditions as may be desirable to facilitate inthe governing of train movements over the railroad. This function of thesystem. is conveniently termed the trans-mission of indications.

By way of explanation, and without attempting to define the nature orscope of the invention, it may be stated, that in the communicationsystem of this invention, certain adjacent or associated trafficcontrolling devices with their related indications are preferablygrouped in what may be referred to as a field or way station. All suchway stations, throughout the railroad, are connected with the controlofiice by three line wires which are employed to form a stepping circuitand a message circuit.

In the transmission of controls from the control ofiice, for the purposeof operating signals, switches, and the like at a particular waystation, a series of stepping impulses are placed upon the steppingcircuit extending to all the stations, which causes step-by-step meansat thecontrol ofiice and at each of the way stations totake a pluralityof steps. During a number of these steps taken by each step-by-stepmeans, a combination of impulses, conveniently termed a code call, whichis allotted to that station, is transmitted over the message-circuitextending to all the way stations, but effective selecting responsethereto is obtained only at the particular station being called. Aftersuch selection of that station, the remaining steps of the cycle areem,- ployed to transmit both the desired new controls and theindications of that station, as then set up, by impulses placed upon themessage circuit by suitable control means respectively at the controloflice and that way station.

Indications of the position of switches, signals, and the like and theconditions of certain track circuits, are transmittedto the controloffice from the several stations one at'a time. A station, having one ormore new indications to transmit, initiates the system into operationcausing a series of impulses to be placed upon the stepping circuit tooperate the step-by-step means at the control office and at each waystation. During a certain number of the steps taken by the stepby-ste-pmeans, a combination of impulses is placed upon the message circuit, atthat way station, corresponding to its code call which identifies orregisters that station in the control office. After this stationselection or registration has taken place, the remaining steps of thatcycle of operation are taken during which impulses are placed upon themessage circuit in correspondence to the new indications to betransmitted from that station and in correspondence with the controlsfor that station as then set up in the control office.

If more than one station is ready to send in new indications to thecontrol office, these stations are allowed to register themselves andcommunicate their indications, one station at a time, in a sequence ororder determined by their geographic location.

Since, in accordance with this invention, the transmission of newcontrols and the registration of each station desiring to send in newindications is accomplished over the message circuit, an importantfeature of the system of this invention resides in the manner in whichonly one such station is selected for the transmission of new controlsand only one such station having new indications is allowed to registeritself in the control ofiice during a particular operating cycle, withonly one of these functions occurring during a particular operatingcycle of the system.

The communication system of this invention may be said, therefore, to beof the station selective type employing code combinations or code callsfor station selection both for the transmission of controls andindications.

Various other characteristic features, functions and advantages of thesystem of this invention are more conveniently explained and pointed outhereinafter, following the description of one embodiment of the presentinvention and its mode of operation. Many of these features andadvantages will be apparent as the description progresses, and need notbe specifically pointed out in detail.

For the purpose of explaining the nature of the invention, there hasbeen shown in the accompanying drawings, one typical embodiment of theinvention adapted for controlling the switches and signals at the endsof passing sidings on a single track railroad; but the same principlesand functioning of the invention, and the same apparatus and circuitsmay be employed, or may be adapted by obvious modifications, for thecontrol of switches, signals, derails or other traffic controllingdevices for all kinds of track lay-outs, and for the receiving ofindications of the positions or conditions of such trafiic controllingdevices, track circuit occupancy and such other conditions as may bedesirable.

In describing the invention in detail, reference will be made to theaccompanying drawings, in which similar parts throughout the severalViews are designated by like reference characters provided withdistinctive exponents, and in which Figs. 1A and 1B when placed end toend illustrate the apparatus and circuits for the control oifice of acommunication system constructed and arranged according to the presentinvention;

Figs. 2 and 3 illustrate the equipments for two typical way stations ofthe system, having distinctive code calls for their selection;

Fig. 4 shows the arrangement of the line circuits;

Fig. 5 shows a typical table of code combinations of impulses employedfor station selection in the system.

For the purpose of simplifying the illustration and facilitating theexplanation, the various parts and circuits constituting the system havebeen shown diagrammatically andcertain conventional illustrations havebeen employed, the drawings having been made more with the idea ofmaking it easy to understand the principles and mode of operation of thesystem, than with the idea of illustrating the specific construction andarrangement of parts that would be employed in practice. Thus, thevarious relays and their contacts are illustrated in a conventionalmanner, and symbols are used to indicate connections to the terminals ofbatteries or other sources of electric current in place of showing allthe wiring connections to such terminals.

Considering first the general organization of the system, three linewires are employed in the particular form shown, namely, a steppingline, a message line and a common return line. These line wiresextend'from the control office through the several stations, with thestepping line con nected to the common return wire beyond the last waystation (see Fig. 4), while the message line is left open-ended at thelast station. These line wires are employed to form two separatecircuits, with a common return connection (common return line),conveniently termed a stepping circuit and a message circuit.

The stepping line wire includes at each station and at the controloffice, a polar line relay L (see Fig. 4) and the message line wireincludes at each station a back contact of a field control relay FC.

The stepping circuit and the message circuit are both supplied withdirect current from sources located at the control ofiice. The fieldstations do not supply current to the line circuits of the system at anytime. This supply of direct current in the control office for energizingthe stepping and message circuits may be a storage battery with suitabletrickle charge or other charging means, motor generator, or any othersuitable source, the voltage required varying with the number of waystations and the length of the line circuits connecting such waystations with the control office.

A source of direct current is required for each field station forenergizing the local circuits of g the communication system, and foroperating the signals, switches and the like at that station. Storagebatteries, maintained charged through rectifiers from a suitable powerline, are preferably employed for this purpose in accordance with commonpractice.

Such sources of electrical energy which supply current to the circuitslocal to the control oflice and each of the way stations are representedby the use of the conventional battery symbols and indicatingconnections to the opposite terminals of a battery or other suitablesource of direct current; and the current, in the circuits with whichthese symbols are used, always flows in the same direction when therespective circuits are closed. The source of current supply for theline circuits is represented by a battery BT having a center tapconnected to the common return line (see Fig. 1B). This battery has itspositive and negative terminals designated by symbols (3+) and (B-),which are used to designate the connections of various circuits theretothroughout Figs. 1A and IE to simplify the circuits of the controlofiice. It will be noted that where a circuit is indicated as connectedto terminals (13+) and (B) the current flow in such circuits may bereversed in accordance with the conditions to be met, as provided for bythe system of the present invention.

The operations of this communication system are preferably performed byrelays of the tractive armature type. Certain 'of these relays, such asthe line relays L, are of the three-position polarized type, the movablearmature being biased to assume an intermediate or neutral position whenthe relay winding is deenergized. When such polar relay is energized,the armature assumes one or the other of two opposite extreme positionsin accordance with the direction of current fiow in its winding. Thecontacts for these relays have been shown conventionally, and forconvenience it is assumed that the contact fingers assume right handextreme positions by the application of positive current and assume lefthand extreme positions by the application of negative current. Some ofthese relays are of the two position polar type, similar to thethree-position polar type relay with the omission of the means biasingtheir contacts to intermediate deenergized positions. The contacts ofthese two-position polar type relays remain in the position to whichthey are last energized even after their windings are subsequentlydeenergized. The contact fingers for these two-position relays aresimilarly. shown in a conventional manner, and are assumed to ,be movedto right-hand extreme positions'by the application of positive current,and to left-hand extreme positions by the application of negativecurrent.

All other relays are of the neutral type, shown conventionally, and arepreferably of the type employed in telephone practice. Certain of theserelays require two windings in accordance with their use in thecircuits, and certainothers require slow releasing characteristics whichare obtained in the usual manner by the use of short circuited windingsassociated therewith. All of these relays are constructed according tothe usual engineeringpractice having suitable characteristics for theirvarious uses as employed in the circuits according to the presentinvention, quick operation of all relays being desirable except in thecase of those relays having slow acting characteristics asconventionally illustrated by heavy base lines on such relays.

The control ofiice equipment.--The equipment for the control ofliceincludes in general a suitable control machine provided with manuallyoperable levers, a track diagram, indicating lamps,

and the like, so as to enable the operator by simple manipulation tocontrol the signals, switches and the other trafiic controlling devicesof the system at the various way stations, and also have before himinformation of the response of such trafiic controlling devices, and ofthe occupancy of various track sections, such as Will enable him tohandle the traffic over the system to the best advantage.

No attempt has been made to illustratetheconstruction of the controlmachine or the arrangement of parts preferably employed; but themanually operable control levers, the track diagram, indicating lamps,various relays and electrical connections have been diagrammaticallyillustrated to explain the function and operation of such systemconstructed according to the present invention, regardless'of itsparticular application in practice.

In the control office (see Fig. 1A) two manually operable levers SGL andSML are respectively provided for operating the signals and the switchat the west-endof a passing siding represented in the control office bya miniature passing siding on a track diagram. The lever SGL is of thethree-position type having contacts I0 and H which make contact withtheir respective fixed contacts when in one of three positions; whilethe lever SML is of the two-position type having a movable contact [2which makes contact with its respective fixed contacts when in extremepositions only. These levers are representative of all the manuallyoperable levers on the control machine employed for the control ofvarious traffic controlling devices in the field, each such lever beingprovided with what is termed a momentary contact, in this case contactsl3 and M for levers SGL and SML respectively, for momentarily closing acircuit as these levers are moved from any one of their positions toanother.

The miniature track diagram, corresponding to the actual track lay-outin the territory under the supervision of the operator, is preferablymade a part of the control machine positioned adjacent to the controllevers for each of the several field stations. As representative of sucha track diagram, the passing siding s is intended to represent an actualpassing siding S in the field, such as shown in Fig. 2 of theaccompanying drawings, and is located over its associated control leversSGL and SML.

Directly above the west end of this miniature passing siding s islocated an indicator lamp I,

which, when lighted, indicates the occupied con,-

dition of a detector track section at the corresponding end of thepassing siding S in the field. This lamp is controlled by an indicationstoring relay IS. It is to be understood that various other indicatorlamps, or other means, can easily be employed to indicate the positionof the switches, the condition of the signals and other similarconditions, such means being controlled in a similar manner, as shownfor the indicator lamp 1.

Associated with each station is a storing relay SR, which is controlledby the momentary contact on each of the control levers included for thatstation. In other Words, these storing. relays register the operation ofa control lever of the corresponding way station and remain energizeduntil the new control set up by such movement of the control lever hasbeen transmitted. A

Each of the storing relays SR has a corresponding code determining orselecting relay CD. These code determining relays CD are energized bytheir respective storing relays SR. and are arranged in a bank havingtheir circuits so interlocked with the storing relays SR. that only onecode may be superimposed upon the message circuit during any particularcycle of operation of the system. The particular one of these codedetermining relays CD, which is superior to the others, when energized,conditions the system for operation to cause the transmission of a codecall characteristic of its corresponding station, in a manner more fullyexplained hereinafter.

Associated with each of the way stations is a message channel steppingrelay bank, two such banks being shown in Fig. 1A for the respective waystations shown in Figs. 2 and 3. Y

The control office equipment includes a code channel stepping relay bankhaving associated therewith a group of code responsive relays. When thesystem is set into operation the relays of the code channel steppingrelay bank operate sequentially closing code channels for the respectivecode responsive relays, which respond to the code being received orbeing sent in a manner to transfer the stepping operation from the codechannel stepping relay bank at the end of the last code step to theparticular message channel stepping relay bank corresponding to the codecall characteristic received by the code responsive relays. The relaysof the selected message channel stepping relay bank then sequentiallystep through to the last message channel step at which tim the systemreturns to its normal at rest condition, if there are no more newcontrols to be transmitted or new indications to be received.

Thus, the control machine in t e control office for each fie1d stationincludes two levers SGL, SML, a portion of track diagram with itsindicating lamps, a storing relay SR, a code determining relay CD, aplurality of indication storing relays IS, and a message channelstepping relay bank.

The stepping relay banks count off the steps during each operating cycleof the system, relays preferably being employed for this purpose, butany other step-by-step mechanism could be used. In the arrangement shownproviding for three station selecting or code steps (capable ofselecting eight stations) and four control and indication steps, thereare five stepping relays in the code channel stepping relay bank,namely, relays 1, 2, 3, 5, and a last code step relay LC; and there arefive stepping relays in each of the message channel stepping relaybanks, namely, relays 5, 6, 1, 8, and a last message channel steppingrelay LM (for way station No. 1). It should be understood that this isonly one arrangement and that the number of steps would be determined inaccordance with the number of stations in use and the number of controland indication steps required for the various individual way stations.

The group of code responsive relays includes relays a, b and c, whichare energized or left deenergized by their respective code channels.These code channels are set up by the code channel stepping relay bank.

The control ofiice equipment also includes suitable means for applyingimpulses of positive and negative polarity alternately, at time spacedintervals, to the stepping circuit. While a motor driven commutator orequivalent means might be employed, two impulsing relays IR and IE areused, each of these relays having slow acting characteristics inaccordance with the time period desired to be marked off.

The control office equipment further includes a line relay L a slowacting relay SL, a cyc e controlling relay CC, a starting relay S, alocal starting relay LS, a field starting relay FS, an a field controlrelay fc.

The relays of the control oifice are interconnected by variouscontrolling circuits, buses, jumpers, and the like which will bediscussed more in detail during the description of the operation of thesystem.

Field station equipment-With reference to Fig. 2 of the accompanyingdrawings, the signals l--I A and 22A with the track switch TS at thewest end of a passing siding S are shown as merely illustrative orrepresentative of the trafilc controlling devices which may becontrolled and from which indications may be received as one fieldstation.

The switch points TS are operated by a suitable switch machine SM, suchfor example as disclosed in the patent to W. K. Howe, No. 1,- 466,903dated September 4, 1923, which is supplied with operating current from alocal battery and which is preferably equipped with a dual controlselector permitting hand operation of the switch points as disclosed inthe patent to W. K. Howe, Patent No. 1,852,573, datedApril 5, 1932. Theoperation of this switchmachine SM is controlled by a function controlrelay SMR of the two position polar type, the energization of this relaybeing under the control of the operator through the agency of thecommunication system of the present invention. The operation of theswitch machine SM is also governed by suitable approach and releaselocking means (not shown) such as disclosed for example in theapplication of W. W. Wenholz et al., Ser. No. 409,- 103, filed November22, 1929, so that irrespective of the operation of the switch machinefunction control relay SMR the switch points TS may not be improperlyoperated.

Train movements over the switch TS are governed by the signals I--|A and2--2A which are controlled by the condition of the associated trackcircuits, the position of the switch points, and in accordance with theposition of the function relays DR and SGR, which are under the controlof the operator for respectively determining in what direction trafficshall be established and whether or not the signals shall indicate clearfor that direction. The circuits for controlling these signals inaccordance with track conditions and the position of the switch pointsare not shown, but may be of the type shown and described for example inthe application of S. N. Wight, Ser. No. 120,423, filed July 3, 1926.

A detector track section TK is associated with the track switch TS andis provided with the usual track battery [5 and track relay T toindicate the condition of occupancy of this track section.

According to the present invention, the communication system equipmentfor each field station includes the same arrangement of relays and thesame circuits connecting the relays except in the case of certainjumpers or connections which may be rearranged or set to fit theparticular code call characteristic of the station at which theequipment is located. These relays included within the communicationpart of the system of the present invention, are preferably housed in aportable cabinet or the like, so that they may be quickly detached incase of trouble to allow a new station unit to replace the old one.

The similarity between the various way station equipments is illustratedby the fact that the same reference characters have been applied to bothFigs. 2 and 3 with similar parts having distinctive exponents, the onlydifference between these stations being the positions of certain jumperswhich feature will be more specifically described hereinafter.

The field station equipment includes a line relay L; a slow acting relaySL; a change relay CH; a field control relay FC; a. code channelstepping relay bank having relays l, 2, 3, 4, and a last code step relayLC; a message channel stepping relay bank having relays 5, 6, 1 and 8; agroup of code responsive relays including relays A, B, C, and a coderesponsive control relay CR. It is to be understood that the number ofstepping relays is merely illustrative and will vary according topractice in accordance with the number of stations and the number ofindications and controls desired to be transmitted.

The change relay CH is provided to be energized momentarily each timethe detector track relay T drops or picks up; but it should beunderstood that the change relay may depend upon several way stations.

a change in position or condition of the signals,

track switch, or other track circuits in a similar manner so thatvarious other indications, when provided, may be transmitted to thecontrol offioe.

The field control relay F is energized when a particular field stationinitiates the system into operation. This field control relay has twofunctions, the first of which is to condition that stationin a mannerso'that it may dictate the impulses placed upon the code or stationselecting steps of the operating cycle to accomplish its own selectionand its registration in the control ofilce; and second, to open themessage line to subsequent way stations preventing interference from anyother station which may be similarly conditioned at that time andendeavoring to send in indications.

With this explanation of the equipment and general organization of thesystem, it is believed zofithat the nature, the various characteristicfeatures and functions of the system will be best understood by furtherdescription being given from the standpoint of operation.

Operation of the system ;;can arise in practice.

- The system is normally at rest with the step ping circuit, includingthe stepping line and the common'return line, deenergized, and with themessage line having energy applied to it at the control office althoughno circuit is completed at this time.

During the time that the system is at rest or in a period of blank, itmay be initiated into operation from the control office or any one ofthe When thus initiated. into operation, the system operates through apredetermined number of steps comprisingan operating cycle, after whichthe system returns to its normal or at rest condition'in readiness forthe next initiation.

The means for impulsing the'stepping circuit is located in the controlofiice, so that the system may be initiated at the control oflicedirectly by starting this impulsing means; but when. the I system isinitiated from a way station, the message line, which isnormally'op'en-ended, is con-- nected by the change relay to the commonreturn line at the particular station having new indications totransmit, which causes current to flow in a message circuit so as toinitiate the im- '75? such initiation conditions that station in suchpulsing means.

Each operating cycle includes the selection of a particular Way station;the transmission of controls for that station as set up by thecorresponding control levers in the control omce; and the transmissionof indications for that station as set up by the position of the trafficcontrolling devices located at that station.

If the system is initiated from the control office, every station issubsequently conditioned to receivecode call impulses, and theparticular station having a code call corresponding to the impulseswhich are transmitted from the control oifice is then selected so thatthe controls and indications associated with that station may also amanner that subsequent thereto a combination of impulses correspondingto the code call of that stationis transmitted by that station, therebyselecting that station and registering it in the control oiilce, so thatthe'controls and indications associated with that station may also betransmitted. This functioning of the system is conveniently termedin-coming station selection.

Thus, each cycle of operation may be said to include five parts, namely,initiation into operation, conditioning for out-going or in-comingstation selection, station selection by the transmission of codeimpulses, transmission of control impulses, and the transmission ofindication impulses.

The transmission of control and indication impulses occurs during eachoperating cycle. If the system is initiated from the control oflice, thecontrol impulses included in the resulting cycle of operation are newcontrols, while the in dication impulses included within that cycle arerepeated as formerly transmitted; but if the sys-' tem is initiated froma way station, the indication impulses included in the resulting cycleof operation are new indications, while the control impulses includedwithin that cycle are repeated as formerly transmitted. This repetitionof controls and indications serves to check each way station. each timeit is selected.

Thus, the description of the operation of the system of the presentinvention conveniently divides itself into two sections, namely, adescription of the transmission'of new controls or outgoing stationselection, and a description of the transmission of new indications orin-coming station selection. Following the description of these twofunctions of the system, their interrelation and co-action will beexplained.

. Outgoing station selecti0n.With the system at rest or in theperiod ofblank, the operator may accomplish the control of any traffic con-'trolling device over which he has supervision, by moving thecorresponding control lever to a suitable controlling position. Thisoperation of a control lever from a former position to a new position isregistered or stored by a storing relay SR which in turn energizes acode determining relay CD, a local starting relay LS, a starting relay Sand a cycle controlling relay CC. The system then operates through acycle, due to a predetermined number of impulses placed upon thestepping circuit.

This energization of the storing relay SR corresponding to the waystation with which the control lever is associated, and the energizationof the corresponding code determining relay CD, determines that theresulting cycle of operation shall be one for out-going stationselection, which may be best explained by considering the detailoperations involved.

For convenience let us assume that the operator desires to operate thetrack switch TS at the first way station (see Fig. 2) from a normalextreme position to a reverse extreme position so that traffic mat berouted from the main track onto the passing siding S, or vice versa, inaccordance with subsequent control of the governing signals.

Manual starting.To operate the track switch TS, the operator moves thecontacts of the control lever SML to their extreme upper positions, andin so doing momentarily closes the contact l4 thereby energizing thestoring relay SR through a circuit from through momentary contact l4,wires 11, I 8 and I9, winding of relay SR to Immediately, when thecontacts of the relay sR 'assume" energized positions, a'

stick circuit for this relay is completed from through back contact 20of relay CD wire 2|, front contact 22 of relay SR wires 23'and I9,windingof relay SR to The energization of the relay SR closes anenergizing circuit for the code determining relay CD from back contact39 of relay SL, wire 3!, front'contact 32 of relay SR wires 33 and 34,winding of relay CD wire 35, back contact 36 of relay LM, to

When the contacts of the code determining relay CD assume energizedpositions, this relay completes its own stick circuit from through backcontact 37' of relay LM, wires '33 and 39, front contact 46 of relay CDwires 4! and 34,

Winding" of relay CD wire 35, back contact 36 of relay LM, to Also, atthis time, the stick circuit of the relay SR v is transferred from backcontact 20 of relay CD through'front contact 29 of relay CD to thecontrol'of back contact 3? of relay LM, which circuit is now traced fromthrough back contact 31 of relay LM, wires 38'and 42, front contact 29of relay CD wire 2|, front contact 22 of relay SR wires 23 and I9,winding of relay SR to In this connection it is noted, that the contact29 -of relay CD is preferably of the make-be'fore-break type, that is, acircuit from the heel of this contact through its back point is notopened until a circuit from the heel of this contact through its frontpoint is completed, and vice versa, thus maintaining the stick circuitof the relay SR closed during the actuation of'the relay CD At the sametime that the code determining relay CD is energized, the local startingrelay LS is energized through a circuitfrom through front contact 45 ofrelay SR wires 45 and 41, upper winding of relay LS, to Immediately uponthe energizationpof the relay LS its stick circuit is" closed fromthrough back contact 59 of relay LM wire 5|, back contact 52 of relayLM, wires' 53*"and 54,- front" contact 55 of relay LS, lower winding ofrelay LS, to The energization of the local starting relay LS closes theenergizing circuit'for the starting relay S from through back contact 58of relay SL, wire 59, front contact 69 ofrelay LS, wire BI,

\ winding of relay S, to'

The energization of the starting relay S closes the pick-up circuit forthe cycle controlling relay CC from frontcontact 62 ofrelay S, wires 63and 64, winding of relay CC, to cycle controlling relay CC is then stuckup through a stick circuit from through back contact 59 of relay LM wire5|, back contact 52 of relay LM, Wires 53 and 65,1front contact 55 ofrelay CC, wires 61 and B4, winding of relay CC, to

Energization of the cycle controlling relay CC closes its front contactIll, thereby conditioning the stepping line circuit in readiness forreceiving impulses of alternate polarity to operate the step-by-stepmeans located at the control oifice and at each of the way stations. 7

The relay CC also closes an energizing circuit for the relay 1R fromthrough front c0ntact II of relay CC, wire I2, back contacts I3, 14, I5and 16 of relays"l, 2, 3, 4 respectively, wire ll, back contacts 18, I9,89, 8| and 82 of relays 5, 6, "I, 8 and LMrespectively, wire 83, backcontacts 84, 85, 86, 8'! and 88 of relay 5 6 1 8 and LM respectively,through similar contacts of the message channel stepping relay Thisbanks corresponding to the other stationstof the system, through the:bus: wire 90, back contact 95' of relay 1R winding of relay R to Theenergization of the relay 13 causes positive potential to be applied tothe stepping line circuitfronr the positive terminal of the battery BTindicated as (B+) through back contact 96 of relay 1R frontco-ntact 91of relay IRA, wires 98 and 99, front contact IQ of relay CC, Wire I99,winding of'relay L, through the stepping line toithe several stationsincluding therein the line relays L at each of those stations, to thecommon return line at the last station, thence to the mid-point ofbattery BT (see Fig. 4).

The energization of the stepping circuit causes the step by step'means(shown as relays) at the control office and at each of the way stationsto take one step, as hereinafter pointed out. This energiz'ation' of thefirst stepping relay at the control office and at each way stationoccurs during the interval of time existing between the actuation of thepolar contact of the line relay L" to its right-hand. energized positionand the response of the contacts of the slow acting relay SL thereto.

In the control office, the energization of the first stepping relayopens the formerly traced energizing circuit of relay 1R at back contact13 of relay I, which Would then cause the relay IE to be deenergized andas soon as the contacts of this first stepping relay assumed energizedpositions, thus causing the first positive impulse on the steppingcircuit to be of insufficient duration to energize the relays SL.

But, the relay 1133' is maintained energized until the relay SL hasassumed an energized position, due to a holding circuit including afront contact of relay I and a front contact of the starting relay S.This circuit may be traced from through a front contact II of relay CC,wire I2, front contact 13 of relay I, wire IIlI, front-contact I02 ofrelay S, wire I03 to bus 90, back contact 95 of relay IR winding ofrelay 1R to When the'relay SL is: energized, the relay S is deenergizedat back contact 58, thereby breaking the holding circuit of the relay 1Rat front contact I82 of relay S and completing the energizing circuitfor the relay IR? from front contact?! of relay CC, wire 12, frontcontact I3of relay I, wire IOI, back contact I02 of relay S, wire I04 tobus 9|, back contact I05 of relay IE winding of relay 1R to Theenergization of the relay 1R causes negative potential to be applied tothe stepping circuit from the negative terminal of the battery BTindicated as (B-) through front contact I U! of relay 1R back contactI98 of relay IR wires I99 and 99, front contact III of relay CC, wireI95, winding of line relay L, through the stepping circuit'as heretoforetraced to the mid-point of battery ET.

The energization-of the stepping circuit with negative potential causesthe polar contacts of the line relays L to'be operated to left handpositions, causing the step-by-step means at the control office and ateach of the Way stations to take the second step.

' The en-ergization of the second stepping relay 2 in the controlo-iiice deenergizes the stepping relay I thereby opening the energizingcircuit of the relay "1R at front contact I3 of relay I". As soon as therelay IE is deenergized, which is an appreciable length of time afterthe deanergization of the relay I, the bus 99 is energized through frontcontact M of relay 2 thereby energizing the relay 1R tive potential uponthe stepping circuit causing the step-by-step means at the controloflice and at each of the way stations to take the third step. In asimilar manner as the relays I" and 2 have alternately energized thebuses 90 and 9 I, likewise the subsequent stepping relays, such asrelays 3, 4, 5, 6, 1, 8 and LM cause these buses 90 and 9| to bealternately energized, resulting in the alternate energization of therelays IR and IE respectively, to place impulses of alternate polaritiesupon the stepping circuit. When the last message channel stepping relayLM, such for example as LM is energized, the stick circuit for the relayCC is opened at the respective back contact (in this case back contact52) thereby deenergizing it, which in turn removes the current supplyfor the impulsing relays IR at front contact 'II of relay CC, causingthe impulsing of the stepping-circuit to cease. v

As We have now considered the manner in which the step-ping circuit mayreceive impulses of alternate polarity, we shall now consider the mannerin which the application of these imipulses to the stepping circuitcauses the stepby-step means at the control ofiice and at each waystation to sequentially and synchronously operate.

Step-by-step operation-From. the above description, it can be seen thatthe manual starting of the system causes the application of the firstimpulse to the stepping circuit, while the response of the step-by-stepmeans in the control office causes the application of the secondimpulse. Hence, the impulsing of the stepping circuit and the operationof the step-by-step means are interdependent.

However, for convenience let us consider that the manual starting causesthe first impulse to which the step-by-step means responds, thus causingthe second impulse, and so on as above explained, in order to observehow the step-bystep means at the central office and at each way stationresponds to such impulses.

For convenience, the code channel stepping relay bank at the first waystation (see Fig. 2) will be more specifically considered in pointingout the operation of the stepping relay banks, although it is to beunderstood that the operation of every stepping relay bank is identicaland may be readily understood by analogy.

With the first impulse of positive polarity placed upon the steppingcircuit, the contacts of the line relay L are energized to right-handextreme positions energizing the relay SL from through contact H0 ofrelay L in a righthand position, wire III, winding of relay SL, to Asthis first impulse is of relatively long duration in respect to thefollowing impulses the slow acting relay SL receives current for asufficient period of time to actuate its contacts to energizedpositions.

During the time that the line relay L is energized and the contacts ofthe relay SL have: not yet responded, a pick-up circuit for the relay Iis closed from through contact II5 of relay L in a right-hand position,wire H6, back contact N1 of relay SL, lower winding of step-- ping relayI, wires H8 and H9, back contact I20 of stepping relay 2, to Thispick-up circuit for the relay I is. closed until the contacts of therelay SL assume energized positions at which time its stick circuit isclosed from front contact I2I of the relay SL, wires I22 and I I23,front contact I24 of stepping relay I, upper This again placesposiwinding of stepping relay I, wires I25 and H9, back contact I20 ofstepping relay 2, .to It is noted in this connection, that the frontcontact I2I is to be preferably closed before the back contact In isopened.

When the relay SL becomes energized with the stepping relay I energized,a circuit is completed from (-1-), through contact II5 of relay L in aright-hand position, wire H6, front contact II! of relay SL, wire I26,front contact I2'I of relay I, lower winding of relay 2, wires I28 andI29, back contact I30 of relay 3, wires I3I, I32 and I22, front contactI2I of relay SL, to It is obvious that both ends of this circuit areconnected to the same terminal of the source thereby leaving thestepping relay 2 unaffected.

However, upon the energization of the line relay L with the oppositepolarity in response to the next impulse on the step-ping circuitfollowing an intervening period of deenergization, negative potential isconnected to this circuit through contact II5 of relay L in a left-handposition. This effectively energizes the stepping relay 2, opening thestick circuit for the stepping relay I at back contact I20 and closingits own stick circuit through front contact I20. This stick circuit forthe relay 2 is traced from through front contact I2I of relay SL, wiresI22, I32 and I3I, back contact I30 of relay 3, wires I29 and I33, upperwinding of stepping relay 2, front contact I20 of stepping relay 2, to

In a similar manner, the energization of the line relay L with alternatepolarities causes the remaining stepping relays 3, 4 and so on to besequentially energized each closing the pick-up circuit of thesucceeding relay and opening the stick circuit of the preceding relay.The point to be noted is, that the closure of a pick-up circuit by apreceding stepping relay is not efiective until the proper polarity isapplied thereto by the line relay upon the next energization of thestepping circuit.

Execution period-This sequential and simultaneous operation of thestepping relay banks at the control office and at each of the waystations is employed to close channel circuits over the message andcommon return lines between the control ofiice and each of the waystations. These channel circuits may then be employed for thetransmission of various conditioning impulses, code call impulses,control impulses and indication impulses in a manner to be hereinafterexplained.

These channel circuits are completed during the time that the steppingline is deenergized, which condition is employed to mark off what isconveniently termed as the message or execution period of each step. Inother words, the energization of the stepping circuit accomplishes theenergization of a stepping relay at the control office and at each ofthe way stations, but the preceding stepping relay must thereafter bedropped out thus causing an overlapping of the steps. However, if thechannel circuits are completed only when the stepping circuit isdeenergized, the stepping relays at the control office and at each ofthe way stations are in what may be termed a static condition so thatany circuit completed at that time can not possibly overlap with anyother circuit which may be completed on the next step during a similartime period.

Eacfi impulse placed upon the stepping'circuit, except the first asheretofore explained, is of a durationincluding the energizing time ofthe line relay L, the energizing time of a corresponding stepping relay,and the deenergizing time of the corresponding impulsing relay IR, Whilethe time interval between successive impulses includes the pick-up timeof the corresponding relay IR. During the energization of the linerelays L, the proper stepping relay for that impulse is energized andremains energized until the next step is taken so that during the timeof deenergization of the line relays marking off the execution period,sufficient time may be allowed by the pick-up time of each one of theimpulsing relays IR to insure the operation of the relays controlledover the channel circuits.

Conditioning of field stations for the reception of code cclls.-Thecontrol oflice and each Way station is provided with a group of coderesponsive relays which are controlled through their respective channelcircuits. In order that the proper stat-ion may be selected or chosenfrom among'all of the stations, the corresponding code responsive relaysat the control office and at each station must be connected in multiplebetween the message line and the common return line on correspondingsteps, but as such a multiple connection of the code responsive relaysis undesirable at the way stations during an in-coming station selectingcycle of operation, each Way station must be conditioned at thebeginning of an out-going station selecting cycle in order that its coderesponsive relays will be eifectively governed by the code impulsesplaced upon their respective channel circuits.

This conditioning of each station for the reception of code impulses orcode calls at the beginning of an out-going station selecting cycle, isaccomplished on the first channel circuit completed when the firststepping relay at the con trol ofiice and at each of the Way stations isenergized. If this channel circuit is energized then every station isconditioned for the reception of code calls; While, if this firstchannel circuit is not energized, no station is conditioned for thereception of code calls.

As the system for this operating cycle under consideration has beeninitiated from the control oifice, the field control relay is at thecontrol oifice is deenergized, this deenergization causes this firstconditioning channel circuit to be energized.

In other words, the system has been manually started or initiated intooperation from the control office resulting in the energization of thefirst stepping relay at the control office and at each of the waystations, upon which step a channel circuit is completed during theexecution period of the step, that is, with relays IR and IR.deenergized, from the positive terminal of the battery BT indicated as(13+), through back contact Md of relay fc, wire MI, front contact I42of relay I, wire hi3, back contact I44 of relay 1R wire I45, backcontact I46 of relay IR wire I41, front contact I48 of relay SL throughthe message line to every way station (at the first way station forexample), through wire I50, front contact I5I of relay SL, wire I52,front contact I53 of stepping relay I, wire I 56, lower Winding of relayCR, wires I55, I56, I51 and I58, to the common return line, and thenceto the mid tap of the battery ET. A similar circuit at each way stationfrom themessage line through its corresponding code response con.-trolling relay CR is completed to the common return line. Thus, theenergization of this channel circuit accomplishes the energization ofthe relays OR at each of the way stations in multiple,

thereby conditioning every station for the reception of code calls asdetermined in the control ofiice.

The code response controlling relay CR is maintained energizedthroughout the cycle of'operation by a stick circuit completed fromthrough front contact IZI of relay SL, Wires I22, I32, I34, I35, I36,I37, I38 and I39, upper winding of relay CR, front contact I49 of relayCR, to A similar circuit is completed for the respective code responsecontrolling relay CR at each of the other stations.

Transmission and reception of code calls.As the relay CR "at each of theway stations is energized, the code responsive relays at the waystations are connected in multiple across the message line and thecommon return line through their respective channel circuits. Althoughany number of stepping relays could be employed having a correspondingnumber of code responsive relays, only the stepping relays 2, 3 and 4have been shown as having code responsive relays A, B and Crespectively. It is evident that each of these code responsive relays A,B and C,

may be energized or left deenergized on its respective step, thusproviding eight combinations which maybe assumed by the contacts ofthese relays by suitably arranging their energizing impulses. Theseeight combinations have been represented by symbols in a Typical tableof codes (see Fig. 5), a symbol representing the energized condition ofthe corresponding relay or a symbol representing the deenergizedcondition of that relay.

With reference to the Typical table of codes (see Fig. 5), a code callrequiring the three code responsive relays A, B and C to be energized isrepresented by code call No. 1 and further denotes that the channelcircuits for these three code responsive relays should each be energizedin order to select the station having that code call assigned to it.Similarly, the code call No. 7, for example, indicates that therespective channel circuits for the code responsive relays A, B and 0should be deenergized, deenergized and energized in. order to select thestation having that code call characteristic.

For this particular cycle of operation under consideration, the controllever SML in the control ofiice has been operated resulting in theenergization of the code determining relay CD which must provideenergization of proper code channel circuits to select the first waystation (see Fig. 2). This first way station has been assignedarbitrarily the code combination or code call symbolically representedin the Typical table of codes (see Fig. 5) by code call No. 3, whichrequires that the first and third code channel circuits shall beenergized to energize relays A and C. In accordance with this, codejumpers I60 and I62 have been provided so that when the code determiningrelay CD is energized, the first and third code channels (closed whenstepping relays 2 and 4 are energized and the stepping line isdeenergized) may be energized.

Considering that the stepping relay 2" in the control ofiice and thestepping relay 2 at each of the way stations are energized, then duringthe execution period of that step, a code channel is completed forenergizing the code responsive relay a in the control office and thecorresponding code responsive relay A at each of the way stations fromthe positive terminal of the battery BT indicaed as (3+), through codejumper I60, front contact I63 of relay CD Wire I64, back contact I65 ofrelay fc, wire I66, lower winding of relay a, wire I61, front contactI68 of stepping relay 2, back contact I42 of stepping relay I", wireI43, back contact I44 of relay 1R wire I45, back contact I46 of relay 1Rwire I41, front contact I48 of relay SL, through the message line toeach of the way stations, (at the first way station for example) throughwire I50, front contact I5I of relay SL, wire I52, back contact I53 ofstepping relay I, front contact I69 of stepping relay 2, wire I10, lowerwinding of relay A, code jumper I80, to the code bus 260, back contactI1I of relay FC, 'code bus 20I, front contact I12 of code responsecontrolling relay CR,

Wires I13, I56, I51 and I58, to the common return line, and thence tothe mid point of the battery BT. Similarly, the relays A A etc., at thesecond, third and remaining way stations respectively are energizedduring this closure of the first code channel circuit, it beingunderstood of course that these relays A at each station are in multipleacross the message line and the common return line.

The code responsive relay A is maintained energized throughout thatcycle of operation by a stick circuit closed from through f'ront contactI2I of relay SL, wires I22, I32, I34, I35, I36, I31, I38 and 2I2, upperwinding of relay A, front contact 2I3 of relay A, to This stick circuitis representative of the stick circuit completed by each of the coderesponsive relays when energized, the respective stick circuits beingcompleted by the corresponding SL relay energized until the end of theparticular cycle of operation.

During the execution period of the next step (third), the code channelcircuit for that step is not energized due to the omission of a suitablecode jumper in the control office (see Fig. 1A), similar to code jumperI60 provided in the case of the first code channel circuit. Thus, thecode responsive relay b in the control oilice and the code responsiverelays B at each of the way stations, remain deenergized.

During the execution. period of the next step (fourth), the code channelcircuit for that step is energized from the positive terminal of thebattery BT indicated as (3+), through jumper I62, front contact I14 ofrelay CD wire I15, back contact I16 of relay f0, wire I11, lower windingof code responsiverelay 0, wire I18, front contact I19 of stepping relay4, back contacts I85, I68 and I42 of relays 3, 2 and I respectively wireI43, back contact I44 of relay 1R wire I45, back contact I46 of relay 1Rwire I41, front contact I48 of relay SL through the message line to eachof the way stations (at the first way station), for example, throughwire I50, front contact H of relay SL, wire I52, back contacts I53, I69and I86 of relays I, 2 and 3 respectively, front contact I81 of steppingrelay 4, wire I88, lower winding of code responsive relay C, code jumperI82, code bus 200, back contact H! of relay FC, code bus 26!, frontcontact I12 of code response controlling relay CR, wires I13, I56, I51and I58, to the common return line, and thence to the mid-point of thebattery BT. Similarly, the code responsive relays C at each of the waystations are energized as they are connected in multiple across themessage and common return. lines.

In a similar manner a larger number of code responsive relays could beemployed but for the purpose of a disclosure of the present inventiononly three such relays have been shown.

, At the first Way station (see Fig. 2 a circuit is completed throughcontacts on the respective relays A, B and C and a chain of connectingcode bank to the message channel stepping relay bank at that station. Atthe second way station and at all other way stations, the contacts onthe relays A, B and C and the chain of connecting code jumpers at thosestations do not complete a circiut for transferring the steppingoperation to the message channel stepping relay banks: at thosestations.

On the fifth impulse of the stepping circuit, the last code channelstepping relay LC at every station is energized and locks up thestepping operation at all of the stations except the first (see Fig. 2),where the stepping relay is energized in multiple with the last codechannel stepping relay LC at that station.

This pick-up circuit for the stepping relay 5 is closed from (-1-),through polar contact H5 of line relay L in its right hand position,wire I I6, front contact I I1 of relay SL, wire I26, back contacts l21,I96 and It of relays I, 2 and 3 respectively, front'contact I92 ofstepping relay 4, wires I93 and I94, front contact I95 of coderesponsive relay A, code jumper 205, back contact I96 of code responsiverelay B, code jumper 266, front contact 591 of code responsive relay C,code jumper 201, wire I98, lower winding of stepping relay 5, wires I99and 2I0, back contact 2II of stepping relay 6, to These message channelstepping relays 5, 6, 1 and 8 are sequentially energized upon theapplication of the corresponding impulses upon the stepping circuit.

As the step-by-step operation. at a particular selected station must betransferred from the code channel step-ping relay bank to the messagechannel stepping relay bank, when the code responsive relays assumepositions corresponding to the code call assigned to that station, thenthe chain circuit through the front or back contacts of the coderesponsive relays must be cornpleted when these relays assume thepositions corresponding to the code call. Thus, it is obvious that thecode jumpers 205, 266 and 281 at each station must be positioned toconnect with the front or back contact of their respective coderesponsive relay in accordance with the code call of that station. Forexample, the jumper 205 should be connected to the front contact of the'certain code jumpers at each station.

As the code jumpers 295, 206 and 261 are arranged in accordance with thecode combinations or code calls, and as a particular combination occursbut once, then it is obvious that with the code responsive relaysassuming corresponding positions at all stations, the chain circuit fortransferring the step-by-step operation from the code channel steppingrelay bank to the message channel stepping relay bank will be completedat but one station.

Should a greater number of stations be employed with the system, agreater number of code responsive relays would be required, three suchcode responsive relays providing eight combinations, four relays sixteencombinations, five relays thirty-two combinations and so on ingeometrical progression with the constant ratio of two.

With reference to the control oifice (see Figs. 1A and 1B), the coderesponsive relays a, b and c are in energized, deenergized and energizedpositions respectively, the relays a and having been energized throughthe same circuits as traced for relays A and C. These code responsiverelays a, b and 0 each have stick circuits closed when they areenergized until the end, of the operating cycle in which they areenergized. For example, the stick circuit of the relay a is closed fromthrough front contact 58 of relay SL, wires 2M, 2l5 and 2H5, upperwinding of relay (1., front contact 211 of relay a, to

A chain circuit is completed by the code responsive relays fortransferring the stepping operation from the code channel stepping relaybank to a message channel stepping relay bank corresponding to thestation which is selected in response to the code call as registeredupon these code responsive relays.

The eight combinations or eight chain circuit selections which may bemade by the code responsive relays a, b and c are brought out to eightsuitable terminals to which the pick-up or lower winding of the firststepping relay in the message channel stepping relay bank of thecorresponding station may be connected. For example, the message channelstepping relay bank for station No. 1 must be connected to theparticular one of the eight terminals that will have the chain circuitcompleted when the code call assigned to the first station has beentransmitted or received. Thus, the lower winding of the stepping relayis connected to the third terminal by a jumper connection indicated by ado-ted line, thereby cornpleting a pick-up circuit for this relay uponthe energization of the line relay L in response to the fifth impulseapplied to the stepping circuit. This pick-up circuit for the steppingrelay 5 is closed from through polar contact 226 of relay L in a righthand position, wire 22 l, front contact 222 of relay SL, wire 223, backcontacts 22%, 225 and 226 of stepping relays l, 2 and 3 respectively,front contact 22'l of stepping relay 4, wires 228 and 229, front contact239 of code responsive relay a, back contact 23l of code responsiverelay in, front contact 232 of code responsive relay 0, through jumper233, wire 234, lower winding of stepping relay 5, wires 235 and 236,back contact 237 of stepping relay 6, to Thus, stepping relay 5 isenergized in multiple with the last code channel stepping relay LC andthe relays 6, 5, 8 and LM sequentially step in response to theapplication of their respective impulses to the stepping circuit.

In a similar manner, if the code responsive relays a, b and 0 wereenergized or deenergized in any other code combination, thecorresponding message channel stepping relay bank would thereby beselected, that is, the step-by-step operation would be transferred tothat stepping relay bank.

In the control office, the last code channel stepping relay LC isenergized simultaneously with the first stepping relay of the messagechannel stepping relay bank which has been selected for the particularcycle of operation. ihe energization of the stepping relay LC, opens thestick circuit of the stepping relay 4 at back contact 23%, therebyallowing the contacts of the relay 8 to assume deenergized positionscompleting the message line to the message channel stepping relay bankfor the station selected (in this case the message channel steppingrelay bank for sta tion No. 1). Similarly, at each of the way stations,the last code channel stepping relay LC is energized upon application ofthe fifth impulse to the stepping circuit, thereby opening the stickcircuit of the stepping relay t at every station. This removes the coderesponsive relay C at the respective stations from their multipleconnection to the message line and the common return line. These relaysLC remain energized until the end of the operating cycle through a stickcircuit including front contact 52! of relay SL thereby locking up thestep-by-step operation of each of the stations except the particularstation which J received its characteristic code call. At this sta tionthe stepping relay 5 is energized in multiple with the relay LC at thatstation and the stepby-step operation is transferred to the messagechannel stepping relay bank of that station, as heretofore explained.

Transmission of new contr0ls.-After a station is selected in response tothe transmission of its code call, the step-by-step operation inresponse to the impulses applied to the stepping circuit occurs in themessage channel stepping relay bank at that station. and in the messagechannel relay bank in the control ofiice corresponding to that station.In this particular case, the message channel stepping relay bank at thefirst way station (see Figs. 2 and 1A) will have the respective relays5, 6, l and 8 sequentially step in synchronism with the relays 5, 6, land 8. The eighth step is followed by an extra step for purposeshereinafter pointed out.

Each message channel stepping relay bank in the control ofiice for therespective way station is capable of connecting upon the respectivechannel circuits certain contacts on the levers of the correspondingstation to the message line, in a manner such that the function controlrelays at the way station will be operated through the respectivechannel circuits in accordance with the position of the correspondinglevers of that station located in the control office.

In this case, the control levers SML and SGL, associated with the firstway station, have contacts which control the energizati-on and thepolarity thereof of the message channel circuits completed by themessage channel stepping relay bank for this station. For example, uponthe fifth step of this cycle of operation under consideration when therelays 5 and 5 are energized and the stepping circuit is deenergized tomark off the message or execution period for that particular step, acircuit is completed from the contact 22 of the lever SML through theswitch machine function control relay SMR at the first way stationapplying the proper polarity in accordance with the position of thelever SML.

As the operator moved the lever SlVl'L to a reverse position to operatethe track switch TS to a reverse position, negative potential is appliedfrom the terminal of the battery B'I indicated as (B), through contactif in a dotted line position, wire 2%, front contact 24 of relay 5, wire2 32, back contacts H9, 585, i623 and 442 of relays i, 3, 2 and 5respectively, wire M3, back contact M l of relay 1R wire M5, back.contact MS of relay IE wire Ml, front contact I48 of relay SL, throughthe message line to the first way station, wire I50, front contact 55'.of relay SL, wire 32, back contacts 553, E69, E86 and E8! of relays l,2, 3 and 4 respectively, wire 2%, front contact 264 of stepping relay 5,wire 245, Winding of relay SMR, wire 246, front contact 241 of Steppingrelay 5, Wires 248 and I58, to the common return line and thence to themid-point of the battery ET in the control ofiice.

This application of negative potential to the relay SMR, causes itspolar contact to be actuated to a'left hand dotted line position whichresults in the operationof the switch machine and the controlling of thetrack switch TS to a reverse position, so that traflic may be routedonto or oif of the passing siding S in accordance with the clearing ofthe governing signals IA or 2A respectively.

With the lever SGL in a central position, the second message channelcircuit is not energized during the message or execution period of thesixth step, thereby allowing the polar contact of the direction controlfunction relay DR to remain in a position as formerly actuated.

However, the third message channel circuit is energized with negativepotential with the lever SGL in a central position during the message orexecution period of the seventh step thereby energizing the relay SGRthrough a circuit which may be traced by analogy to the circuit tracedfor the relay SMR. Thus, the polar contact of relay SGR is actuated to aleft hand position, which determines that the signals I-IA and 22A shalldisplay stop indications.

The manner in which these function controlling relays SMR, SGR and DRcontrol their respective traffic controllingdevices is only indicated bydotted lines, it being understood that the control may be accomplishedin any suitable manner, such for example as shown in the patent to S. N.Wight, Patent No. 1,889,457, dated November 29, 1932. It is also to beunderstood, that any number of function control relays may be employedfor operating various other traffic controlling devices the same as, ordifferent, than those illustrated, these relays being operated inaccordance with control contacts in the control office over messagechannel circuits provided by extra stepping relays.

If some other station had been selected, such for example as the secondway station shown in Fig. 3, a. message channel stepping relay bankcorresponding to that station in the control office would besequentially operated in synchronism with the message channel steppingrelay bank at the second way station. The channel circuits set 'upthereby would be governed by similar control levers SML and SGL (notshown) associated with the second Way station. In other words, thegroupof levers corresponding to each station is associated with acorresponding group of message channel stepping relays beingpermanentlyconnected 'to the front contacts of the respective relaysclosing the proper channel circuits provided thereby. I

Transmission of old indications-As this cycle of operation was.initiated in response to the movement of a control lever in the controlofiice, it can be easily seen that one or more of the controls resultingtherefrom will. be new controls, but in all probability the indications,transmitted during such a cycle of operation, will be old indications,that is, indications transmitted in accordance with the position oftraffic controlling devices at that way station prior to thetransmission of the controls, and as formerly transmitted.

Upon the seventh step, or more generally speaking, upon the steppreceding each particular step assigned for the transmission of anindication impulse, a; resistance is included in the stick circuit ofthe corresponding stepping relay in the control office. A drop inpotential occurs across this resistance during the execution period ofthat step which is employed to actuate the polar contact of anindication storing relay IS to a normal position. If on the next step,during the completion of its message channel circuit, the indicationcontact at the way station which governs this relay, is closed, then thepolar contact of this indication storing relay will be actuated to anopposite or reverse position. This actuation will not be cancelled untilthe station is again selected, in order toinsure that the indicationwill be stored and be a true indication of the position of the governingindication contact at the way station. If the governing indicationcontactv is not closed, then this polar contact will remain in itsnormal position as: controlled by the potential drop across theresistance.

This has been more specifically pointed out for the indication storingrelay IS which has a resistance R connected in series with the stickcircuit of the stepping relay 1. When current flows through this stickcircuit including the resistance R, a drop in potential is createdacross the resistance which causes current to flow from its left handterminal through wire 25%, lower winding of relay IS, wire 25!, to theright hand terminal of this resistance. It is to be understood ofcourse, that the source of supply furnishing current for the stickcircuit, also furnishes this-current for the relay IS. This flow ofcurrent actuates the polar contact of relay IS to a left-hand position(as shown).

During the message or execution period of the eighth step, a channelcircuit is closed or left open in accordance with the positon of thecontacts of the trackrelay T. In this case, there is no train upon thedetector track section 'IK, therefore the track relay T will beenergized. Thus, this indication channel circuit will remain openallowing the polar contact 252 of relay IS to remain in its left handposition, as actuated by the drop in potential across the resistance R.

If this circuit had been closed due to the deenergization of the trackrelay T, this polar contact 252 of the relay IS would be operated to aright hand position and indicate the occupied condition of the detectortrack section TK by the energization of the indicator lamp I, through acircuit obvious from the drawings.

It is to beunderstood that a greater number of channel circuits can beemployed to provide .a greater number of indication message channelcircuits, so that indication of Various other con.- ditions such asindication of the position of signals, position of switches, and thelike, may be provided for assisting the. operator in directing trafficover that part of the railroad under his supervision.

It is to be understood that indication storing relays similar to therelay IS are to be associated with each way station and are similarlycontrolled over channelcircuits provided by the message channel steppingrelay bank corre sponding to the station with which they are associated.7

End of Operating cycle-After the eighth stepping relay in the messagechannel stepping relay bank in the control oflice corresponding to thestation selected and the corresponding message channel stepping relaybank at the selected station has been energized, another impulse isplaced upon the stepping circuit to cause the last message channelstepping relay LM to be energized. This opens the stick circuit of thestepping relay 8. The relay LM closes its own stick circuit and remainsenergized until the re lay SL is deenergized, but it also opens thestick circuits of the relays SR CD LS and CC at the contacts 37, 36 and52. The deenergiation of. the relay CC opens the stepping circuit atfront contact 'l'll thereby causing the line relays L to remaindeenergized. The starting relay S cannot be energized as long as therelay SL is energized; and; the stepping line cannot be energized untilthe relay CC is energized by the relay S. Hence, as the stepping lineremains deenergized another cycle of operation cannot be initiated untilthe relay SL has been deenergized, which occurs a predetermined timeperiod after the last energization of the line relay L This in.- suresthat the relays SL at every station will be deenergized, at which timethe system will be restored to a normal at rest condition, even ifanother cycle is to be initiated. However, if no control lever is movedor no new indication occurs at a way station, the system remains atrest.

Sequence of outgoing station selection-It will be evident that the coderesponsive relays at each of the stations are capable of assuming butone combination of energized and deenergized positions, whichcombination is assumed in accordance with the particular channelcircuits which are energized during the station selecting part of theoperating cycle. Should two or more code calls or combinations ofimpulses be applied to the message line during the station selectionpart of the operating cycle, then the code calls would be mutilated andcause the selection of some station unintentionally.

This mutilation of code calls may be best understood with referencebeing made to the Typical table of codes (see Fig. 5). If the code callNo. 3, provided for the first way station, and the code call No. 6,provided for the second way station, are combined, it is obvious thatthe code call No. 6 is the one which is actually existent during thestation selecting part of the operating cycle. Thus, the station havingcode call No. 6 assigned to it is unintentionally selected anderroneously controlled.

Of course the operator could be relied upon to actuate a lever for theselection of a particular station and then allow sufficient time for thecontrols to be transmitted in accordance therewith before operatinganother lever; but such a procedure would considerably handicap theoperator in planning train movements and limit the extent of theterritory which one operator could adequately supervise.

In accordance with the present invention, means is provided, whereby thecontrol levers for the various stations may be moved simultaneously orin rapid succession, with said means automatically determining thesequence of the transmission of the proper code calls to prevent anymutilation thereof.

This means, which determines the sequence of out-going station selectionby determining the code calls which are transmitted, includes a storingrelay SR for each group of levers associated with a particular station,which storing relay is energized when any one of the levers of thatparticular group has been operated to a new position. Ihe energizationof a storing relay SR, energizes its corresponding code determiningrelay CD when. the system is at rest, or in a period of. blank whichoccurs between two cycles of 0peration. Each of these code determiningrelays CD provides that the code call of its corresponding station istransmitted with the character of the code call determined by itsassociated code jumpers, such for example as the code jumpers I60 andl62 associated with the first way station. However, the circuitscontrolled by the code determining relays CD and associated code jumpersare so interlocked that the impulses of only one code call may betransmitted over the message line during the station selecting part of aparticular operating cycle.

If more than one of the code determining relays CD is energized at atime, the code jumpers corresponding to the particular energized codedetermining relay CD which is farthest to the left, are caused to governthe energization of the code channel circuits; while the code jumpers ofthe other code determining relays (which are energized) to the right ofthe above mentioned code determining relay do not effect the codechannel circuits. At the end of the operating cycle this particular codedetermining relay, which determined the code call for that cycle, isdropped out and the next code determining relay to the right of it whichis energized determines the call for the succeeding cycle of operation.

This may be best understood by assuming that both the relays CD and CDare energized (see Fig. 1A). The code jumpers I69 and I82 are thenconditioned to control the code channel circuits as heretofore pointedout. However, the code jumper 2Bl associated with the relay CD cannoteffect the code channel circuit of. the third step, due to the openingof back contact I84 of relay CD nor can either of the two other codechannel circuits be effected by the code determining relays and codejumpers to the right of the relay CD due to the open condition of backcontacts I63 and H4.

It is obvious that when the relay CD is deenergized the wires I64, 255and H5 will then be connected to wires 256, 251 and 258 permitting thenext code determining relay to the right (which is energized) to thencontrol the code channel circuits. In other words, the code channelcircuits pass through chain circuits including contacts on the codedetermining relays CD, in a manner that when a particular relay isenergized, it is effective to prevent the control of every codedetermining relay to the right of it.

These code determining relays CD may be picked up when the relay SL isdeenergized as heretofore pointed out in connection with relay CD Thus,the particular code determining relay to the left, which is lastenergized during the time that the system is at rest or in a period ofblank, is the one to transmit or determine the code call for thesucceeding cycle of operation. The energization of the relay SL preventsthe mutilation of a code call during transmission.

If the operator moves several levers while the system is in operation,the corresponding storing relays SR are energized, but the codedetermining relays CD corresponding to those storing relays are notenergized until the end of that cycle of operation, at which time theyare energized upon deenergization of the relay SL; but these codedetermining relays CD transmit the code calls in a sequence or orderfrom left to right.

It is of course to be understood, that these relays SR do not have to beassociated in an order in accordance with the geographic location of thestations, but each one of these storing relays may be associated withany way station desired. For convenience the storing relay SR has beenassociated with the group of levers for the first Way station, thestoringrelay SR has been associated with the group-of levers for thesecond way station (not shown), and so on; but these storing relays SRSR could be associated with the other groups of control levers therebychanging the order of sequence in which the code calls of the respectivestations are transmitted.

Incoming station selection.The selection of stations for thetransmission of out-going controls, the transmission of these controlsand the repetition of the indications associated therewith, is allaccomplished, as above explained, over the message circuit. Also, thesame message circuit is employed for the transmission or communicationof impulses to accomplish station selection for incoming indications,the transmission of those indications and the repetition of the controlsassociated therewith.

This utilization of the message circuit to transmit impulses in eitherdirection is made possible, due to the manner 11 which the system is.conditioned for either out-going station selection or incoming stationselection.

As there are many trains passing over the system under the supervisionof the operator, these trains may arrive at OS-ing points:simultaneously, thereby providing indications at several stations whichare ready for transmission at the same time. Likewise, the operator maytransmit controls to several stations, the resulting operations beingcompleted at substantially the same time, thereby providing indicationsat the several stations to be transmitted to the control ofiice.However, as only one way station can be in communication with thecontrol ofiice for incoming station selection during a particular cycleof operation, means is provided whereby the station having newindications to transmit which is nearest the control office is madesuperior to the others and locks them out, so to speak, during theinitiation of the system from the field. In other words, the initiationfrom the field is employed as the conditioning period for determiningwhich way station is superior and determining that the cycle ofoperation shall be for incoming station selection. ,Thus, the condiancewith code call transmitted from the field.

For convenience, the selection of a single station and the transmissionof its indications, controls and the like will be explained first, withthe means of look-out for station superiority during incoming stationselection pointed out at a later time.

Automatic starting.Whenever a change takes place in the occupancy of adetector track circuit, the position of a switch, signal or othertrafiic controlling device which is required to provide an indication inthe control ofiice, the system is automatically set into operation forthe selection of the corresponding station. This change in conditions ata Way station is registered by the momentary closure of the pick-upcircuit of the change relay CH at that station.

This momentary energization of the relay CH is sufiicient to actuate itscontacts to energized positions, which completes a stick circuit formaintaining the change relay energized until the corresponding" stationhas been selected and the new indication transmitted.

-For convenience, let us refer to the first way station (see Fig. 2) andconsider in detail the operation of the system when initiated from thefield due to a change in detector track circuit occupancy, such anoperation being considered as representative of all such operationswhich might occur due to a change in position of a signal, track switchor the like at this station or any other station.

The passage of a train onto or off the detector track section causes thecontacts of relay T to assume deenergized or energized positionsrespectively, for reasons well understood. ,This movement of thecontacts of the relay T causes the momentary or make-before-breakcontact of the relay to complete a circuit from through momentarycontact 265 of relay T, wires 266 and 261, winding of relay CH, to Thisenergizes the relay CH causing a stick circuit to be closed from throughback contact 268 of stepping relay 5, wire 269, front contact 218 ofrelay CH, wires 21! and 261, winding of relay CH to With the system atrest, the energization of the relay CH shorts the message line to thecommon return line thereby completing a circuit from (B-|-), throughback contact 212 of cycle controlling relay CC, Wire 213, Winding offield starting relay FS, wire 214, back contact 215 of relay SR wire216, back contact 211 of relay SR wire 218, back contact I48 of relaySL' through the message line Wire to the first way station, wire I58,back contact I5| of relay SL, wire 219, front contact 280 of relay CH,wire 28I, upper winding of relay FC, Wires 282, 283, I51 and I58, to thecommon return Wire and thence to the midpoint of battery ET. The closureof this starting circuit energizes the field starting relay FS in thecontrol ofiice and the field control relay FC at this way station. Thefield control relay FC is maintained energized, until that station hasbeen selectively operated, by a stick circuit closed from through backcontact 291 of relay 8, wire 298, front contact 299 of relay FC, lowerwinding of relay FC, to In a similar manner, the field starting relayF'Sand the relay FC at any other way station can be energized in seriesshould the change relay at some other station become energized with thesystem at rest.

The energization of the field starting relay FS closes a pick-up circuitfor the local starting relay LS from through front contact 284 of, relayFS, wires 285 and 41, upper winding of relay LS, to The relay LS becomesenergized and closes its stick circuit, and also energizes the startingrelay S, which in turn energizes the cycle controlling relay CC, all ina manner as heretofore pointed out for manual starting. Thus, the systemis initiated into operation as the result of the change in the conditionof occupancy of the detector track section TK at the first Way station.The energization of the change relay CH at that station for any otherchange in condition of traffic controlling devices, or the change relayat any other station, would result in a similar automatic initiation ofthe system.

Energization of the field starting relay FS also accomplishes theenergization of a field control relay fc in the control office fromfront contact 286 of relay FS, wires 281 and 288, winding of relay fc,to This relay closes its stick circuit from through back contact 289 ofrelay LC, wire 290, front contact 298 of relay fc, wire 288, winding ofrelay jc, to The energization of the cycle controlling relay CCdeenergizes the field starting relay FS at back contact 212, but thisoccurs subsequent to the energization of the relay fc as theenergization of relays FS and S intervene between the energization ofthe relays FS and CC,

The energization of this field control relay ,fc determines that theconditioning channel circuit completed during the execution period ofthe first step shall be deenergized. In other words, the energization ofthe field starting relay FS determines that the cycle of operation isone for in-coming station selection which conditioning of the system isaccomplished during the initiation thereof from the field.

Transmission and registration of code calls from a way station;Assumingthe system to be automatically initiated into operation as aboveexplained and impulses to be placed upon the stepping circuit causingthe sequential and simultaneous operation of the step-by-step means atthe control ofiice and at each way station, we will now consider theselection and registration of the first way station which is now readyto send in new indications.

During the execution period of the first step, the channel circuit forthat step is deenergized. Thus, the relay CR at each of the way stationsis left deenergized. This means that the code responsive relays at eachof the way stations, except the way station where the relay FC isenergized, are not connected to the message line and common return lineon their respective channel circuits as explained for out-going stationselection, as the front contact I12 of the relay CR is open.

However, the relay FC at the first way station, where the change hasoccurred resulting in the initiation of the system from the station, isenergized. The energization of this field control relay FC closes itsfront contact I1I which connects those code responsive relays, which arenecessarily energized for the selection of that station, through theirrespective channel circuits to the message line and the common returnline. In the control ofiice the energization of the field control relayis causes positive potential to be applied to the message line from thebattery ET on each of the code channel circuits. Thus, during theexecution period of those steps where the channel circuits have the coderesponsive relays connected to the message line and the common returnline, a circuit is completed which energizes the corresponding coderesponsive relays in the control ofiice and at the station which istransmitting the code call.

More specifically, during the execution period of the second step, acircuit is completed from the positive terminal of battery BT indicatedas (B+), through front contact I65 of field control relay fc, wire I55,lower winding of code responsive relay a, wire I61, front contact I 68of stepping relay 2, back contact M2 of stepping relay I, wire I43, backcontact I44 of relay 1R wire Hi5, back contact I46 of relay 1R wire I41,front contact I48 of relay SL, through the message line to the first waystation, wire I50, front contact i5I of relay SL, wire I52, back contactI53 of counting relay I, front contact I69 of stepping relay 2, wireI10, lower Winding of code responsive relay A, code jumper I80, throughcode bus 200, front contact I1I of relay FC, wires 283, I51 and I 58, tothe common return line and thence to the mid-point of battery BT. Thus,the code responsive relays a and A, at the control office and at thefirst way station respectively, are energized and maintained energizedthrough their stick circuits.

During the execution period of the third step, positive potential isapplied to that channel circuit through front contact 292 of relay I0and the code responsive relay b, but the code jumper I8I at the firststation connects the code responsive relay B to the code bus 20I whichinasmuch as front contact I12 of relay OR is open, this channel circuitis not completed during the execution period of this third step.

However, during the execution period of the fourth step, inasmuch as thecode jumper I82- is connected to the code bus 200 at the first waystation, the channel circuit for that step is completed to permitcurrent to flow from the positive terminal of the battery BT indicatedas (13+), through front'contact I16 of relay fc, wire E11, lower windingof code responsive relay 0, wire I18, front contact I19 of steppingrelay 4, back contacts I85, I68 and I42 of stepping relays 3, 2 and Irespectively, wire I 23, back contact I44 of relay 1R wire I05, backcontact Hit of relay 1R wire I41, front contact I48 of relay SL, throughthe message line to the first way station, wire I50, front contact I5Iof relay SL, wire I52, back contacts I53, I55 and I85 of stepping relaysI, 2 and 3 respectively, front contact I81 of stepping relay 4, wireI88, lower winding'of code responsive relay 'C, code jumper 582, codebus 200, front contact I1I of relay FC, wires 283, I51 and I58, to thecommon return line and thence to the mid-point of battery BT.

Thus, the group of code responsive relays in the control oflice areenergized and ole-energized in correspondence with the group of coderesponsive relays at the first way station, both groups assumingpositions in accordance with the code call of the first way station.This correspondence causes the step-by-step operation at the controlofiice and at the first way station to be transferred from therespective code channel stepping relay banks to the message channelstepping relay banks corresponding to the first way station.

Fromfthe above description it can. be seen, that each, of the channelcircuits, having code responsive relays connected therein, receiveenergy in the control ofiice due to the energization of the fieldcontrol relay fc, while the actual completion of each channel circuit isdependent upon the position of the respective code jumper at the waystation connecting that channel to either the code bus 200 or 20L If thecode/jumper connects the channel circuit to the code bus 200, thatchannel circuit is closed and current flows therein to pick up thecorresponding code responsive relays at the control ofiice and at theway station; while if the code jumper connects that channel circuit tothe code bus 20L that channel circuit is not closed and current does notflow therein.

For example, the first way station has the code call No. 3 (see Fig. 5)assigned to it which requires the respective channel circuits of thecode responsive relays A, B and C to be energized, deenergized andenergized. In, accordance with this code call, the code jumpers lat andI82 are connected to the code bus 2530, thereby causing the respectivechannel circuits to be closed and energized upon their respective steps,while the connection of the code jumper I8I to the code bus 20I causesits respective channel circuit to be deenergized. In other words, thecode jumpers I80, I8I and I82 at each station must be arranged inaccordance with the code call of that station, each code jumper beingconnected to the code bus 2M3 if its channel circuit is to be energizedas rep-resented by a symbol in the Typical Table of Codes, while if suchchannel circuit is to be deenergized as represented by a symbol thenthat code jumper is connected to the code bus 2M.

Transmission of old controls.Upo-n the application of the next impulse(fifth) to the stepping circuit for this cycle of operation, the lastcode channel stepping relay LC at the control office and at each of. theway stations is energized. At the control office the 'code responsiverelays a, band 0 are assuming positions in. correspondence with the codecall of the first Way station, hence upon the application of this fifthimpulse, the stepping relay 5 will be energized in multiple with therelay LC.

At the first way station the code responsive relays A, B and C areassuming positions in correspondence with the code call of that station,

therefore upon the application of the fifth impulse the stepping relay 5will be energized in multiple with the last code channel stepping relayLC, in a manner as heretofore pointed out. At all other way stations asthe'code responsive relays at those stations are all deenergized thestepby-step operation will be discontinued with the energization of therelays LC at those stations.

Upon the energization of the relay LC in the control office, the fieldcontrol relay fc is deenergized due to the opening of its stick circuitat back contact 285 of relay LC.

At the first way station the change relay CE is deenergized upon theenergization of the stepping relay 5 due to the opening of back contact258. As this stepping relay 5 is deenergized upon the next step, thechange relay is then con.- ditioned for storing such other changes inposition of traffic controlling devices at that station as may occur,subsequent to this fifth step.

The step-by-step operation of the system continues in a mannerheretofore explained, closing the control channel circuits for therelays SMR, DR and SGR, causing them to be controlled in accordance withthe positions of their corresponding levers in the control office. It isnot considered necessary to describe and specifically point out thechannel circuits for the function control relays SMR, DR and SGR, nor toassume certain positions for the control levers, as such operations havebeen previously explained.

However, it is to be noted in this connection, that in practice thelever SGL would bein such a position as to have previously caused theclearing of one of the signals I--IA and 2-2A in order for a train topass onto the detector track section TK. However, it is to be assumedthat such a condition or some other similar condition exists and thatthe controls in accordance therewith have been previously transmitted.Thus, the closure of the channel circuits for the control of thefunction control relays SMR, DR and SGR is a repetition and serves tocheck and maintain these function control relays in their previouslyoperated positions.

Transmission of new indications;--Assuming the system. to operate up tothe eighth step as previously explained, the indication storing relay ISis energized on the seventh step by the drop in potential across theresistance-R which-insures that the contact 252 is actuated to a lefthand position.

If the track relay T is deenergized, the channel circuit closed duringthe execution period of the eighth step will be energized; but if thetrack relay is energized, that channel circuit will remain deenergized.If the channel circuit is energized, the polar contact 252 of theindication storing relay IS will be operated to a right hand positionenergizing the indicator lamp I in the control oflice, indicating theoccupied condition of the detector track section TK in accordance withthe shunted or deenergized condition of the track relay T. Thisenergized condition of the indicator lamp I will exist, although thestation is again selected causing the indication storing relay IS to beenergized by the drop in potential across the resistance R, if the trackrelay is still deenergized, as the indication storing relay IS wouldagain be energized through its respective channel circuit on the eighthstep to again actuate the polar contact 252 to a right hand position.

For convenience assuming that the track relay is deenergize'd asheretofore pointed out to accomplish the energization of the relay CI-I,this indication channel circuit closed during the execution period ofthe eighth step from the positive terminal of the battery BT indicatedas through upper winding of indication storing relay IS, wire 300, frontcontact 30I of stepping relay 8, back contacts 302, 353 and 24I ofstepping relays 'I, 6, and 5 respectively, wire 242, back contacts I19,I85, I68 and I42 of stepping relays 4, 3, 2 and I respectively, wireI43, back contact I44 of relay 1R wire I45, back contact I46 of relay 1Rwire I4'I, front contact I48 of relay SL, through the message line tothe first way station, through wire I50, front contact I5I of relay SL,wire I52, back contacts I53, I69, I86 and IB'I of stepping relays I, 2,3 and 4, wire 243, back contacts 244, 304 and 385 of stepping relays 5,5 and I respectively, front contact 306 of stepping relay 8, wire 301,back contact 308 of track relay T, wire 305, front contact 31s ofstepping relay 3, back contacts 3I I, 3I2 and 241 of stepping relays I,6 and 5 respectively, wires 248 and I58 to the common return line, andthence to the mid-point of battery BT.

Also, upon the energization of the eighth stepping relay, the stickcircuit for the field control relay PC at Lthe first way station isopened at back contact 2 91 of stepping relay 8.

End of operating cycZe.Upon the application of the next impulse (ninth)to the stepping cirwit, the last message channel stepping relay LMincluded in the message channel. stepping relay bank for station No. 1,is energized. The energization of this stepping relay causes thedeenergizatio-n of the local starting relay LS and the cycle controllingrelay CC, thus causing the sys tem to be returned to the at rest orperiod of blank condition in a similar manner, as explained for the endof an out-going station selection cycle of operation.

When the train passes off the track section TK, the change relay CI-IWill be again energized causing the system to operate through anothercycle of out-going station selection. Such a cycle of operation will besimilar to the one just explained with the exception that the indicationchannel circuit of the eighth step will not be' energized. This willleave the polar contact 252 of relay IS in a left hand position to whichit is actuated on the preceding step (seventh). Other operations will beunderstood by analogy.

